Method of forming a fuel cell stack

ABSTRACT

A method of forming a fuel cell stack, wherein the stack includes an anode electrode layer, an adhesive and anode gas diffusion layer coupled to the anode electrode layer, an ion exchange membrane coupled on a first side to the gas diffusion layer opposite the anode electrode layer, an adhesive and cathode gas diffusion layer coupled to a second side of the ion exchange membrane, and a cathode electrode layer coupled to the adhesive and cathode gas diffusion layer opposite the ion exchange membrane. The fuel cell stack may be flexible.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of and claims priority to U.S.application Ser. No. 11/933,997, entitled Method of Forming a Fuel CellStack, filed on Nov. 1, 2007, the contents of which hereby incorporatedherein in its entirety for all purposes.

BACKGROUND

Similar to batteries, fuel cells function to produce electricity throughchemical reactions. Rather than storing reactants as batteries do, fuelcells are operated by continuously supplying reactants to the cell. In atypical fuel cell, hydrogen gas acts as one reactant and oxygen as theother, with the two reacting at electrodes to form water molecules andreleasing energy in the form of direct current electricity. Theapparatus and process may produce electricity continuously as long ashydrogen and oxygen are provided. While oxygen may either be stored orprovided from the air, hydrogen gas may be generated from othercompounds through controlled chemical reactions rather than storinghydrogen, which may need to be compressed or cryogenically cooled. Asfuel cell technology evolves, so do the means by which hydrogen gas isgenerated for application with fuel cells.

One means by which hydrogen gas is generated is through reactivechemical hydrides. This process involves chemically generating hydrogengas from dry, highly reactive solids by reacting them with water.Chemicals especially suitable for this process are lithium hydride,calcium hydride, lithium aluminum hydride, sodium borohydride andcombinations thereof, each of which is capable of releasing plentifulquantities of hydrogen.

It has been found that the reaction products from the chemical hydrideand liquid water typically form a cake or pasty substance whichinterferes with further reaction of the reactive chemical with theliquid water or acid. Furthermore, the reaction of chemical hydrideswith liquid are difficult to control, and generally results in theproduction of much more hydrogen gas than needed to power smallelectronic devices.

In order to combat this problem, methods have been introduced wherein ahydrogen fuel can be reacted with gaseous water vapor, instead of liquidwater. In many hydrogen generator designs, an elaborate power generatorsystem is used in order to regulate the quantity of water vapor thatreacts with the chemical fuel and to regulate the reaction rate of watervapor with the chemical fuel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross section representation of a fuel pellet according toan example embodiment.

FIG. 2 is a cross section representation of a power generatorincorporating a fuel pellet according to an example embodiment.

FIG. 3 is a cross section representation of chemical hydride for a fuelpellet being fissurized according to an example embodiment.

FIG. 4 is a cross section representation of a multiple segments ofchemical hydride for a fuel pellet being fissurized according to anexample embodiment.

FIG. 5 is a cross section representation of a plurality of segments of afuel pellet having a bore according to an example embodiment.

FIG. 6 is a cross section representation of a cylindrical fuel pellethaving multiple bores according to an example embodiment.

FIGS. 7A and 7B are cross sections of a top and bottom portions of apower generator having a fuel cell stack according to an exampleembodiment.

FIG. 7C is a partial cut away of a perspective view of the top of thepower generator illustrated in FIG. 7A

FIG. 8 is a top view of an anode mask according to an exampleembodiment.

FIG. 9 is an illustration of multiple patterned anodes having holesaccording to an example embodiment.

FIG. 10 is a blown up view of a pattern of FIG. 9 according to anexample embodiment.

FIG. 11 illustrates an adhesive layer with an anode gas diffusion layeraccording to an example embodiment.

FIG. 12 represents an ion exchange membrane layer according to anexample embodiment.

FIG. 13 represents a double sided adhesive layer including a gasdiffusion layer for a cathode layer according to an example embodiment.

FIG. 14 illustrates a cathode pattern having electrodes with holesaccording to an example embodiment.

FIG. 15 illustrates an anode mask according to an example embodiment.

FIG. 16 illustrates multiple anode patterns using the mask of FIG. 15according to an example embodiment.

FIG. 17 is an exploded perspective view of a fuel cell stack accordingto an example embodiment.

DETAILED DESCRIPTION

In the following description, reference is made to the accompanyingdrawings that form a part hereof, and in which is shown by way ofillustration specific embodiments which may be practiced. Theseembodiments are described in sufficient detail to enable those skilledin the art to practice the invention, and it is to be understood thatother embodiments may be utilized and that structural, logical andelectrical changes may be made without departing from the scope of thepresent invention. The following description of example embodiments is,therefore, not to be taken in a limited sense, and the scope of thepresent invention is defined by the appended claims.

A fuel pellet is described that is comprised of chemical hydride, metalhydride, and a selectively permeable membrane. The chemical hydrideportion of the fuel pellet may be segmented into a number of parts withgas spaces in between to facilitate transport of water vapor andhydrogen. In one embodiment, the chemical hydride evolves hydrogenspontaneously upon exposure to water vapor, and the metal hydridereversibly adsorbs/desorbs hydrogen based on temperature and hydrogenpressure. In various embodiments, the chemical hydride of the fuelpellet provides a large store of releasable hydrogen for a fuel cell,and the metal hydride provides higher levels of hydrogen for pulseintervals of higher demand. The selectively permeable membrane is awater impermeable and hydrogen and water vapor permeable membrane. Itmay also provide some containment to help the fuel pellet keep a desiredshape, and also to prevent fuel particles from leaving the pellet andcontaminating the power generator. Desired shapes include those suitablefor existing and future common form factor batteries. In furtherembodiments, the fuel pellet may be fissurized to further facilitatewater vapor and hydrogen transport.

FIG. 1 illustrates a fuel pellet 100 that includes multiple segments110, 112, 114, 116, and 118, the fuel pellet 100 may be formed of anon-fluid, hygroscopic, porous material. Such a pellet may be useful inhydrogen gas generating power generators that incorporate one or morefuel cells. A power generator may include a fuel chamber within agenerator housing that holds the fuel, which may be encapsulated orwrapped in a water impermeable, hydrogen and water vapor permeablematerial 130. Reaction of the fuel with water vapor produces hydrogengas that is used by the at least one fuel cell to generate electricity.

In one embodiment, the fuel pellet comprises a non-fluid, hygroscopic,porous material in pellet form that allows for the diffusion of gasesand vapors. Materials which may be used non-exclusively include alkalimetals, calcium hydride, lithium hydride, lithium aluminum hydride,lithium borohydride, sodium borohydride and combinations thereof.Suitable alkali metals non-exclusively include lithium, sodium andpotassium. When contacted with water molecules, these fuels react,releasing hydrogen gas. The fuel may optionally be combined with ahydrogen generation catalyst to catalyze the reaction of the water vaporand the non-fluid substance. Suitable catalysts may non-exclusivelyinclude cobalt, nickel, ruthenium, magnesium and alloys and combinationsthereof.

The fuel pellet 100 may be used in a power generator 200 illustrated incross section in FIG. 2. A fuel cell layer 210 may be wrapped around thefuel pellet 100. A membrane 215 may be disposed within a container 220that is responsive to pressure differences between the inside of thepower generator 200 and ambient to regulate the generation of hydrogenvia valves, which may be integral with the fuel cell layer 210, orotherwise disposed within container 220. The fuel cell layer 210 may beelectrically coupled to a cathode 225 and anode 230 positioned indesired locations, such as on either end of the container 220.

In one embodiment, the container 220 has a shape adapted to beconsistent with desired common battery shapes, such as “AA”, “AAA” “C”and “D” cells. The fuel pellet may have a cylindrical shape and also maybe adapted to be consistent with the desired shape. Other shapes ofcontainers may also be provided consistent with other battery shapesexisting or new battery shapes.

In one embodiment, the fuel pellet may be fissurized to increase thesurface area of the pellet to allow penetration of water vapor. Afissurized pellet is a pellet that has been crushed to have cracks, andmay be into pieces, but still keeps a desired form. Overall porosity maybe increased. The fissurized pellet has fissures that allow the watervapor to diffuse into the pellet, effectively increasing the surfacearea the pellet presents to water vapor.

A device 300 for fissurizing a pellet is shown in cross section in FIG.3, with a pellet 310 placed into a fixture 320. Fixture 320 is providedwith an opening 325 that provides a chamber for the pellet 310 thatprevents the pellet from changing shape as it is fissurized. A piston330 or other impacting device is thrust toward an exposed surface of thepellet 310, causing multiple fissures 340 to occur. The representationof the fissures 340 in FIG. 3 is not meant to be representative of theactual appearance of fissures within a pellet. The force of the pistonmay be such that fissures are created without significantly modifyingthe shape of the pellet, allowing it to retain its form when removedfrom the opening 325. In one embodiment, the force of the piston issufficient to cause a significant number of water vapor penetrablefissures to effectively increase the surface area of the pellet,allowing the pellet to provide a higher rate of hydrogen on demand.

Other methods of causing such fissurization of a pellet may be used,such as different forms of pistons, or different types of impacting. Inone embodiment, cycles of heating and cooling may be used, and mayinclude the use of a temperature responsive solvent to create thefissures.

A similar device 400 is illustrated in FIG. 4. Multiple pellet segments410, 412, 414 and 416 are illustrated in a fixture 420. A water vaporpermeable, water impermeable membrane 422 is provided around the pellet.Fixture 420 is provided with an opening 425 that provides a chamber forthe pellet that helps prevent the pellet from changing shape as it isfissurized. A piston 430 or other impacting device is thrust toward anexposed surface of the pellet, causing multiple fissures 440 to occur.The force of the piston may be such that fissures are created withoutsignificantly modifying the shape of the pellet, allowing it to retainits form when removed from the opening 425.

In one embodiment, the force of the piston is sufficient to cause asignificant number of water vapor penetrable fissures to effectivelyincrease the surface area and porosity of the pellet, allowing thepellet to provide a higher rate of hydrogen on demand. In oneembodiment, the force may be increased due to the ability of themembrane 422 to help the pellet maintain its shape. In one embodiment,the fissurized pellet is soaked in the hydrophobic material whichpenetrates at least some of the fissures to help prevent significanthydrogen generation if the pellet is exposed to liquid water.

Further details regarding the water vapor permeable, liquid waterimpermeable material 130 are now provided. The water vapor permeable,liquid water impermeable material 130 may comprise any material havingsuch properties, and includes porous polymer films and fabrics, as wellas oils and rubbers. The fuels may be encapsulated using any suitablemethod which would be appropriate for the chosen encapsulation material,such as wrapping, coating and the like. In one embodiment a layer of awater vapor permeable, liquid water impermeable material is wrappedaround the fuel, and optionally the ends of the fuel.

In one embodiment, the water vapor permeable, liquid water impermeablematerial 130 comprises a micro-porous polymeric film. Such polymericfilms non-exclusively include mono- and multilayer fluoropolymercontaining materials, a polyurethane containing materials, polyestercontaining materials or polypropylene containing materials. Suitablefluoropolymer containing materials include polytetrafluoroethylene(PTFE) and expanded polytetrafluoroethylene (ePTFE), PFA, FEP. Examplefluoropolymer containing materials are films and fabrics commerciallyavailable under the Gore-Tex®, eVent® and HyVent® trademarks. Gore-Tex®is an e-PTFE material commercially available from W.L. Gore andAssociates of Newark, Del., and eVENT® is a PTFE material manufacturedby BHA technologies of Del. HyVent® is polyurethane containing materialcommercially available from The North Face Apparel Corp., of Wilmington,Del. Of these, ePTFE GORE-TEX® materials are preferred.

Each of these materials may be in the form of single or multilayer filmsor fabrics, or as coatings, and are known as waterproof, breathablematerials. Breathable membranes are typically constructed from amicro-porous layer of expanded PTFE, polyurethane or polypropylene thatis laminated to the face of a film such as nylon or polyester.Breathable coatings are typically formed by spreading a thin layer of amicro-porous or hydrophobic polymer directly on the surface of amaterial, such as the solid fuels of the invention. Breathability isgenerally measured in two ways. In one method, the water vaportransmission rate of a material may be tested as a rating in grams ofhow much vapor a square meter, or alternately 100 in², of fabric willallow to pass through in 24 hours (g/m²/24 hours or g/100 in²/24 hours).Conventional testing methods include the procedures set forth in ASTME-96 Method B and the procedures set forth in ASTM F1249. The secondmethod is known as Evaporative Resistance of a Textile (RET). The lowerthe RET, the higher the breathability, i.e. the greater the amount ofmoisture that will pass through. Based on an ASTM E-96 Method Bbreathability, rates of 100-10000 g/m²*24 h, 500-2000 g/m²*24 h, and700-1200 g/m²*24 h. Other rates may also be used, both within the rangesdescribed, and outside of such ranges.

The micro-porous materials generally have a pore size of from about0.001 μm to about 1 μm in diameter, and a thickness of from about 0.1 μmto about 100 μm. The porosity and thickness of the materials can betailored to give a desired water vapor flux, while preventing liquidwater penetration. In one embodiment, the films or fabrics have a poresize consistent with obtaining a desired overall moisture permeability.In some embodiments, the pore size may range from about 0.01 μm to about5 μm. Larger or smaller pore sizes may be utilized in conjunction withother design parameters to obtain a desired overall moisturepermeability.

In another embodiment, the water vapor permeable, liquid waterimpermeable material comprises a micro-porous oil or rubber coating. Inone embodiment, a hydrophobic material is used that soaks into thepellet, preventing rapid release of hydrogen if the pellet is damagedand the interior is exposed to liquid water. Such materials may includePTFE dispersions and other materials such as oils that may soak into apellet, preventing rapid release of hydrogen if the pellet is damagedand exposed to liquid water. Oils may non-exclusively include mineraloil, petroleum based oils consisting primarily of saturatedhydrocarbons, oily solvents such as xylene, paraffin wax. Such rubbersnon-exclusively include curable rubber, isoprene, silicone,polyurethane, neoprene, and fluoropolyether based rubbers. Anyconventional coating method may be used to encapsulate the fuel with amicro-porous oil or rubber coating. For example, a fuel may be mixedwith an oil or rubber solution, a solvent and a curing agent to form ablend, which blend is warmed and stirred to a desired consistency,granulated, dried and optionally pelletized. Suitable solvents forforming an oil or rubber solution non-exclusively include ketones suchas methyl ethyl ketone, methyl isobutyl ketone, ethers, and ester.Suitable curing agents non-exclusively include organosilanes containingat lease one isocyanate group. Such blends may be formed in a suitablevessel at a temperature of from about 0° C. to about 1000° C., or fromabout 20° C. to about 500° C., and dried for from about 1 to about 24hours. Other granulation and pellet forming techniques may also be used.

Similar to the films described above, the porosity and thickness of theoil or rubber coating materials can be tailored to give a desired watervapor flux, while preventing liquid water penetration. In oneembodiment, the oil or rubber coating materials have a pore size of fromabout 0.001 μm to about 1 μm, or from about 0.01 μm to about 0.5 μm, orfrom about 0.05 μm to about 0.1 μm. Further, in one embodiment, the oilor rubber coating materials have a thickness of from about 0.01 μm toabout 10 μm, or from about 0.05 μm to about 5 μm, or from about 0.1 μmto about 1 μm.

While the fuels described are particularly well suited for use in apower generator apparatus, the encapsulated fuels may be used withvirtually any type of power generator device that is designed to utilizein-situ generated hydrogen gas.

Pellet Manufacturing

In one embodiment, fifty grams of fine lithium aluminum hydride powdermay be mixed in 100 ml hexane and approximately 0.1 grams of a curablerubber solution. The curable rubber solution includes a curing agent.The mixture may be warmed in a hood to 500° C. and stirred. The mixturemay be stirred continuously as it is warmed, until the entire mixtureshas a soft, rubbery consistency. The soft mass may be removed from thehood and granulated over a 400 mesh sieve. The granules are collectedand dried at approximately 600° C. in an air oven in a hood forapproximately 8 hours. The dried granules are pelletized in a press andready for use. This is just one example method for preparing granulesfor a pellet. The parameters may be varied in further embodiments, anddifferent methods may be used as desired.

In one embodiment, the pellets are solid and approximately 20% porous.The porosity may be varied to control volume expansion and hydrogengeneration rate. Multiple pellet segments may be stacked vertically toprovide a cylindrical pellet with larger height. The height of theindividual segments may also be varied to increase the pellet surfacearea, which may also increase the hydrogen generation rate. In oneembodiment, the pellet may be subjected to crushing to further increasethe surface area via fissurization, while still maintaining theircylindrical form.

FIG. 5 is a cross section representation of a further fuel package 500.Fuel package 500 includes multiple chemical hydride fuel pellet segments510, 512, 514, 516, and 518 stacked in a vertical relationship. A watervapor permeable, water impermeable membrane 520 may be disposed aboutthe fuel pellet segments, which may be cylindrical in shape. Themembrane 520 may extend over the ends of the stack of fuel pellets insome embodiments. An air gap may be provided between the membrane 520and fuel pellet if desired.

A bore 530 may be formed in the fuel pellet in one embodiment. The bore530 may extend through one or more segments, or may extend partiallythrough one or more segments. In one embodiment, the bore is concentricwith the axis of the fuel pellet, but may also be parallel, ortransverse to the axis or at any angle therebetween. The bore 530 mayprovide room for expansion of the fuel pellet under varying time andenvironmental conditions.

In a further embodiment, the bore 530 may have a metal hydride porousrod 540 or pellet segments disposed within it. The rod may becylindrical in one embodiment. In further embodiments, the rod 540 maybe shaped consistent with the shape of the bore 530, or may have adifferent shape than the bore 530 to allow for easier migration of watervapor. In one embodiment, the rod 540 is the same shape as the bore tooptimize hydrogen generation. The rod 540 may be used to providehydrogen at a faster initial rate than the pellets in response to a highdemand for power, and may be recharged by excess hydrogen generated bythe chemical hydride portion of the pellet in times of low power demand.

Metal Hydride Preparation Process

The metal hydride fuel may be prepared by first crushing or grindingmetal hydride (in a ball mill, for example) to obtain metal hydrideparticles in the range from 1 um to 1 mm (particles in the range of 10to 100 um are desired in one embodiment). The metal hydride may also beprepared by repeated exposure to high pressure hydrogen (>500 psi) andthen vacuum, which breaks the metal hydride into smaller particles. Theresulting metal hydride may then be heated to >100° C. under vacuum(Pressure<10 mTorr) for several hours. High pressure hydrogen (>500 psi)may be applied for several hours. The heating and high hydrogen pressuresteps may be repeated for several cycles. The metal hydride may beencapsulated using a fumed silica or sol-gel process described below, oralternately coated with copper. The resulting encapsulated or coatedmetal hydride may be molded in a cylindrical pellet form. This is justone example method for preparing metal hydride for a pellet. Theparameters may be varied in further embodiments, and different methodsmay be used as desired.

Encapsulation Process (Fumed Silica Method)

One method which may be utilized to embed or encapsulate metal hydrideparticles in a silica network begins by providing a pre-determinedamount of amorphous fumed silica. This substance may be a high puritysilicon oxide (SiO₂) and is commercially available, such as CAB-O-Sil®grade EH-5 from CABOT Corporation. Fumed silica may be formed by burningsilicon tetrachloride vapor in a flame of hydrogen and oxygen.

In one embodiment, the fumed silica is then blended into water to form apaste via a polymerization process. The weight ratio of water to fumedsilica can range from 3:1 to 9:1. Metal hydride particles are added tothe paste to be embedded into the silica network. The weight ratio ofthe metal hydride particles to the fumed silica in the paste ranges from0.18:1 to 2.3:1. In practice, the metal hydride typically comprises 15%to 70% of the finished product by weight. In one embodiment, the metalhydride particles have sizes ranging from 0.5 μm to 100 μm. In oneembodiment, it is desired that the particles are smaller than 50 μm.Examples of hydrides that can be used in the composition include purehydrides such as Pd and more complex alloys of Pd, Ti, La, Ni, Zr, Coand Al. In further embodiments, metal hydrides may be produced in theform of fine particles.

According to one embodiment, the paste is then allowed to dry to form asolid. The simplest method for drying the paste is to allow it to airdry. However, using heat and/or vacuum drying techniques may provideadditional beneficial properties. Next, the solid composition may beground up using a commercial grinder, grain mill or simply a mortar andpestle. Typically the ground up solid is filtered through a sieve tocollect granules of a desired size for packing into columns or bedscommonly used in hydrogen storage or separations systems.

If desired, the ground up solid can be added back into a new paste offumed silica and then dried and ground up to form a composition having adouble layer of silica with metal hydride particles embedded in thelayers. The process may be repeated to generate a composition havingmultiple silica layers.

Alternatively, the paste can be poured into a mold and then dried usingthe techniques discussed above to form plates, cylinders, or otherdesired forms for use in filtering hydrogen from other gases.

For applications where mechanical strength is critical, the paste can beimpregnated in a porous substrate or wire network and once again driedusing the techniques discussed above. Advantageously, the paste is quiteversatile and is readily adaptable for use in a variety of applications.

According to another embodiment of the invention, greater resistance tooxygen and other impurities, a liquid that is non-soluble in water canbe added to the paste. Examples of such liquids include common paintthinner and mineral oil spirit type 11, grade A. The non-soluble liquidhas the effect of breaking down the paste into particulates that canthen be dried using the techniques discussed above. The following stepsdescribe one example embodiment of the invention incorporating thenon-soluble liquid.

First, acquire 85 grams of fumed silica, 33 grams of LaNi₄.25Al_(0.75)powder (metal hydride) having a particle size .1toreq.45 μm and 351grams of deionized water. The water may then be placed in a blender atmedian speed. Add the fumed silica and the metal hydride to the watergradually until the entire amount is added and a uniform paste isformed. Switch the blender to low speed and pour into the paste 170 ccof paint thinner (non-soluble liquid). Continue blending until the pasteis broken into particulates. The particulates can then be removed fromthe blender and dried using the techniques discussed above. In addition,the particulates can be ground up and run through a sieve to collect apreferred granule size for the final product.

If desired, the final product based on the embodiments discussed abovecan be heat treated in the presence of an inert noble gas such as He orAr to adjust the porosity or mechanical strength of the composition.This heat treating process is known as sintering.

In the final product, the silica particles form a porous network viapolymerization of the silica molecules at contacting points. The size ofthe pores in the network is typically between 1 and 100 nanometers. Incontrast, the metal hydride particles are only 0.5 μm (fines) to 100 μmlarge. Since the metal hydride particles are 5 to 1000 times larger thanthe silica pores, the metal hydride particles are easily retained in thenetwork. When the product is exposed to a gas mixture containinghydrogen and other gases or undesirable impurities, the hydrogen is ableto pass freely through the pores of the network because of its smallmolecular size. Conversely, the larger molecules of the other gases orimpurities are filtered by the silica network from reaching the metalhydride particles held therein. Thus, the product can be freely exposedto the atmosphere without fear of oxidizing the embedded metal hydride.In some embodiments, CO molecules may be filtered with some degree ofsuccess. In addition to acting as a filter, the silica network may alsoprovide dimensional stability to the metal hydrides to curb theirtendency to break into fines after repeated exposure to hydrogen.Although the silica network cannot prevent the formation of finesentirely, any fines that are produced are held within the network andprevented from finding their way into the hydrogen storage equipmentcausing resistance to gas flow or even plugging up the system.

Encapsulation Process (Sol-Gel Process)

In one embodiment of the present invention, a hydride composition may beprepared by a sol-gel process generally as follows. The startingmaterial is an organometallic compound such as tetraethoxysilane. A solmay be prepared by mixing the starting material, alcohol, water, and anacid. The sol is conditioned to the proper viscosity and a hydride inthe form of a fine powder is added. The mixture is polymerized, thendried under supercritical conditions. The final product is a compositioncombining an inert, stable and highly porous matrix with auniformly-dispersed hydride. The composition can rapidly and reversiblyabsorb surprisingly large amounts of hydrogen (up to approximately 30moles/kg) at room temperature and pressure. Hydrogen absorbed by thecomposition can be readily be recovered by application of heat orvacuum.

The composition may be prepared as follows:

1. To prepare the sol solution, add alcohol to water while stirring thewater to form a first mixture. The ratio of alcohol to water in themixture is preferably in the range of two to five parts of alcohol toone part of water. The ratio is chosen in view of the desired propertiesof the final product. For example, the higher the alcohol:water ratio ofthe mixture, the more uniform the final product; and the lower thisratio, the more granular the product. Preferably, the alcohol isethanol, although other alcohols such as methanol may be used.

2. Adjust the acidity of the mixture by adding hydrochloric acid (HCl)until the pH is in the approximate range of 1.0 to 2.5. Stir the mixturefor several minutes, preferably for approximately thirty minutes. Ifdesired, other acids such as hydro sulfuric acid (H.sub.2 SO.sub.4) ornitric acid,(HNO.sub.3) may be used. The pH and temperature of themixture affect the properties of the final product, including itsdensity, porosity, and specific surface area. The optimum conditions forproducing a composition with the desired properties are therefore bestdetermined by observation and a modest degree of experimentation.

3. Separately prepare a second mixture by mixing alcohol and anorganometallic compound such as tetraethoxysilane ((C.sub.2 H.sub.5O).sub.4 Si). Add alcohol to the tetraethoxysilane in the ratio ofapproximately one part ethanol to two parts tetraethoxysilane. Stir forseveral minutes, preferably for approximately thirty minutes. As forstep (1) above, while ethanol is preferred, other alcohols such asmethanol may be used.

Suitable organometallic compounds for use in the present inventioninclude, but are not limited to, organometals of the forms MO_(x)R_(y)and M(OR)_(x), where R is an alkyl group of the form C_(n)H_(2n+1), M isan oxide-forming metal, n, x, and y are integers, and y is two less thanthe valence of M. Other suitable organometals include the alkoxysilanes,particularly tetraethoxysilane. It will be understood that the optimumadmixture of alcohol depends on the particular choice of organometal andthe desired properties of the final product.

4. Add the first mixture to the second very slowly, preferably dropwise,stirring continuously, to form the sol solution.

5. Allow the sol to condition in a closed container for several hours atroom temperature, preferably for about 24 hours.

6. Remove the cover of the container to evaporate some of the solvents,until the sol reaches the approximate viscosity of heavy oil.

7. When the sol reaches the proper viscosity, add a hydride in the formof fine particles, and stir to uniformly suspend the hydride particlesin the solution. The hydride may be added in an amount up toapproximately 50 wt. % of the dry gel. However, the catalytic effect ofthe hydride (discussed below) may be evident even with very smalladmixtures, as small as 1 wt. % or less of the dry gel.

The hydrogen-absorption rate of hydrides is typically proportional totheir surface area. Therefore, the smaller the particle size, the largerthe surface area of the hydride and the better its overallhydrogen-absorption rate. The hydride may be a transition metal hydridesuch as Al, Cu, La, Ni, Pd, Pt, or combinations thereof, and mostpreferably Pt or a La—Ni—Al alloy. The hydride may be supplied in theform of a fine powder having particles less than approximately 100 μm insize.

8. If desired, the density of the sol-hydride mixture can be adjusted byadding a foaming agent. Suitable foaming agents include, but are notlimited to, alkali metal soaps, metal soaps, quaternary ammoniumcompounds, detergents, alkali metal phosphates, and amino compounds.

9. Polymerize the mixture by equilibrating in air at room temperatureand pressure until a gel containing the polymerized material and aliquid as two continuous phases is formed.

Depending on the properties of the sol and the desired properties of thefinal product, polymerization may be carried out at differenttemperatures or pressures, in an inert atmosphere (such as helium orargon), or some convenient combination thereof. For example, lowertemperatures typically slow down the polymerization reaction and may bedesirable to prevent overly abrupt polymerization. The time required forsubstantially complete polymerization varies from a few minutes toseveral days, depending on the temperature, pressure, atmosphere, the pHof the sol, the materials used to produce the sol, and so forth.

The optimum conditions for polymerization are best determined byexperimentation for each particular combination of materials in view ofthe desired properties of the composition. Process steps 1 to 8 asdescribed above may also be carried out at any convenient temperatureand pressure, or in atmospheres other than air, including but notlimited to helium and argon.

10. Dry the gel to remove the liquid phase. Drying may be carried out atthe supercritical conditions of ethanol (or other alcohol produced inthe polymerization process), that is, the temperature and pressure aremaintained at the point where the solid, liquid, and vapor phases ofethanol coexist (243° C. and 63 atm.). Drying under supercriticalconditions can yield a composition with a porosity of 90% or higher.Alternatively, drying may be carried out in air, or in other atmospheresincluding inert atmospheres when a greater density is acceptable.

It will be understood that the process steps described above may bevaried in different embodiments. By way of example only, the solsolution (steps 1 to 6) may be prepared by another suitable procedureknown in the art, or conditioning (step 5) or evaporation (step 6)omitted if the mixture has a suitable viscosity.

The final product is a composition comprising a porous glass matrixcontaining uniformly distributed hydride particles. The matrix is highlyporous, preferably with a porosity greater than 80% porous and mostpreferably greater than about 90%. Because of its high porosity, thematrix has a very large specific surface area, preferably greater thanapproximately 300 m²/gram and most preferably 1000 m²/gram or higher.The composition can be fabricated in the form of pellets or other shapesdimensioned to the anticipated use. The pellets are dimensionallystable, remaining intact after many hydrogen absorption-desorptioncycles.

The higher the porosity and specific surface area of the composition,the more matrix surface and hydride surface is available for hydrogenabsorption. As noted above, the surface of a porous glass compositionnormally absorbs only a small amount of hydrogen. Here, surprisingly,the combination of the aerogel matrix and the hdyride is capable ofstoring very large amounts of hydrogen, more than the sum of theindividual capacities of the aerogel and the hydride. While not wishingto be bound by theory, it is believed that the hydride may act as acatalyst to improve the hydrogen-storage capability of the composition.This catalytic effect should be evident even at very low hydrideconcentrations, as low as 1 wt. % of the dry gel.

By way of example, a composition in a further embodiment may be preparedby adding two parts ethanol to one part water, and adjusting the pH byadding hydrochloric acid. The pH-adjusted mixture is added to a mixtureof approximately one part ethanol to two parts tetraethoxysilane. Thesol is stirred for thirty minutes, then conditioned for about 24 hoursand evaporated until it reaches the approximate viscosity of heavy oil.A hydride in an amount of 40 wt. % of the dry gel is added. The hydrideis La—Ni—Al alloy, preferably in the form of particles less than 100 μmin size in order to promote uniform dispersion throughout the matrix andmore effective contact with hydrogen, in an amount of 40 wt. % of thedry gel. The mixture is polymerized, then dried at room temperature andpressure.

This composition absorbs up to 10 moles/kg of hydrogen at roomtemperature and atmospheric pressure. The amount of hydride present inone kilogram of the composition is capable of absorbing only 5 moles ofhydrogen. Since the aerogel alone can absorb only a negligible amount ofhydrogen, the increased capacity is due to the synergy of the hydrideand aerogel.

Depending on the choice of ingredients and the conditions under whichthe process steps are carried out, the composition may absorb up to 30moles of hydrogen per kilogram at room temperature and pressure, rapidlyand reversibly. Hydrogen absorbed by the composition can readily berecovered by heat or evacuation. Uses for the composition includehydrogen storage and recovery, recovery of hydrogen from gas mixtures,and pumping and compressing hydrogen gas.

Properties and Characteristics of Metal Hydrides

Aluminum substitution in LaNi5 may affect the equilibrium hydrogenpressure, decreasing it with increased substitution. In one embodiment,it is desired to use an aluminum substitution (y value) of between 0.1and 1, which yields an equilibrium pressure at 25 C of ˜1.0-0.1 bar.

Roles of Metal and Chemical Hydride:

In one embodiment, the chemical hydride is the primary, high-densityhydrogen storage material. It generates hydrogen irreversibly whenreacted with water vapor. The rate at which the chemical hydridereleases hydrogen is directly proportional to the delivery rate of watervapor. When pulses of current (power) are required, the consumption rateof hydrogen exceeds the delivery rate of water to the chemical hydride,and thus also exceeds the hydrogen generation rate. In such a situation,the hydrogen is rapidly depleted and the pulse cannot be sustained forlong periods of time. It is desirable to increase the period of time acurrent pulse may be sustained. This is accomplished in one embodiment,by adding a metal hydride (LaNiAl, TiFe, etc) to the chemical hydridefuel pellet. Metal hydrides have the ability to quickly and reversiblyadsorb and desorb large quantities of hydrogen at a relatively constantpressure. Thus, when a current (power) pulse is required, the metalhydride can quickly desorb enough hydrogen to maintain the pulse forlong periods of time. When the pulse is over, hydrogen liberated by thechemical hydride is used to slowly recharge the metal hydride.

In one embodiment, the pellet has a selectively permeable outermembrane/coating. The pellet is an annular porous LiAlH4 fuel pelletwith periodic gaps (bores) in fuel pellet to aide diffusion of watervapor into and hydrogen out of the fuel pellet. The pellet may also havean encapsulated metal hydride in the pellet core. A surrounding layer ofwater reactive LiAlH4 insures that no water vapor reaches metal hydridecore, preventing corrosion/degradation of metal hydride. In oneembodiment, a thermally conductive rod 550 is disposed in the center ofcore 540 proximate and thermally coupled to the metal hydride, andconnecting to the fuel cell can to facilitate heat transfer into and outof metal hydride pellet. The rod 550 facilitates the absorption of heatin the metal hydride, allowing it to desorb (discharge) hydrogen. Rod550 also allows the metal hydride to reject heat to adsorb hydrogen(recharge). In a further embodiment, a porous metal mesh surrounding theencapsulated metal hydride pellet may be used as a heat transfermechanism.

In one embodiment, a plurality of bores may be provided as illustratedin a top view of a fuel pellet 600. A vertical bore 610 along the axisis formed in one embodiment, with other vertical bores 615 and 520illustrated. Horizontal bores 625 and 630 are also illustrated. Boresmay also be formed on angles between those shown in further embodiments.Single or multiple bores at the same or different angles may be utilizedin various embodiments. Selected bores may also contain metal hydride invarious embodiments.

Copper Coating Process:

In one embodiment, the metal hydride may be coated with copper. Withrespect to the process described below, the quantities used in theprocess are scalable, the alcohol is ethanol, CH3CH2OH, or other alcoholbased on input. In one embodiment, LaNiAl is used along with a Cu ratioof 100:5. The ratio may be varied according to the need. Selected stepsmay be performed quickly to minimize evaporation.

Procedure:

In a First Container:

-   1. Dissolve 3.5 g CuSO4 into 50 ml water.-   2. Add 0.5 g EDTA (ethylenediamine tetraacetic acid,    (HO₂CCH₂)₂NCH₂CH₂N(CH₂CO₂H)₂).-   3. Heat at 50° C., agitate for 30 min to form the coating solution.

In a Second Container:

-   1. Wet 27.9 g LaNi4.25Al0.75 powders with 0.63 g (˜0.79 cc) ethanol    (CH3CH2OH).-   2. Add drops of formaldehyde (HCHO), total 1.3 g (˜1.59 cc). Agitate    to make it uniform.

In a Combined Container:

-   1. Combine the wetted LaNi4.25Al0.75 and the coating solution.    Agitate intensively for 10 min.-   2. Filter out the LaNi4.25Al0.75 powders.-   3. Rinse 5 times with DI water. Dry naturally in air.-   4. (optional) Finally, compress the powders into desired shape. Use    a top compressive pressure of 20 MPa.

Manufacturing a Fuel Cell Stack

In one embodiment, a fuel cell stack, such as fuel cell stack 210 may bemanufactured as a thin film. It may be less than one mm thick in someembodiments, and flexible such that it is conformable to many differentshapes. Multiple layers of the fuel cell stack 210 may be rolled orotherwise stacked together, and result in a flexible film that can bebent around the fuel or valves for ease of manufacture. The followinglayers are described for use in a cylindrical battery shape. Otherlayouts of layers may be used to form different shapes. The examplelayouts provide for the formation to two fuel cells coupled in series.

FIG. 7A is a cross sectional representation of a top portion of anexample power generator at 700. Beginning inside power generator 700, ahydrogen generating fuel portion in one embodiment includes a porousmetal hydride 705 within a porous thermal conductor layer 710. Thehydride 705 and conductor layer 710 are disposed within a chemicalhydride 715. These fuels are provided within a selectively permeablemembrane 720.

A fixed valve 725 is disposed around the fuel mixture, and includesmultiple openings such as slots for allowing hydrogen and water vapor topass. Around the fixed valve 725 is a moveable valve 730, havingopenings that selectively line up with or cover the openings in thefixed valve 725.

An anode support 735 surrounds the valve assembly and supports a fuelcell stack 740, that receives hydrogen from the fuel and oxygen fromambient air, and converts them to water vapor and electricity. The fuelcell stack resides within a container 745, that is formed with anexternal cathode electrode 750 that is electrically coupled to a cathodewithin the fuel cell stack via a tab 755. Openings are provided incontainer 745 to supply oxygen from ambient air to the cathode of fuelcell stack 210.

A pressure responsive valve diaphragm 760 is coupled to a valve pin 765,for moving the moveable valve 730 to regulate the flow of hydrogen andwater vapor responsive to electrical demand placed on power generator700. A vent 770 to ambient may be formed in the cathode 750 or otherconvenient location to provide ambient pressure to valve diaphragm 760.

A lower portion of the power generator 700 is illustrated in FIG. 7B,which is numbered consistently with FIG. 7A. An anode output tab 775 iscoupled to an external anode electrode 780. Hydrogen flushing andfilling ports 785 may be provided through the anode electrode 780, and anon-conductive base 790, which may be constructed of the polymer PET inone embodiment. In a further embodiment, a base support layer 787 isformed of metal, such as stainless steel, and provides additionalsupport. In one embodiment, the base support layer 787 functions toprevent the fuel from expanding and pushing out the bottom of the powergenerator 700. It also provides additional mechanical strength(resistance to crushing) to the overall power generator 700.

A partial cut away perspective view of the upper half of the powergenerator 700 is illustrated in FIG. 7C, which is numbered consistentlywith FIG. 7A. In one embodiment, the power generator is cylindrical inshape, and may be formed consistent with form factors associated withcommon batteries for electronics, or other batteries as desired.

In one embodiment, the fuel cell stack 740 comprises an anode electrode791 coupled to an adhesive and anode gas diffusion layer 792. The gasdiffusion layer 720 is coupled to an ion exchange membrane 793, such asa Nafion® membrane, which in turn is coupled to an adhesive and cathodegas diffusion layer 794. The fuel cell stack 740 also includes a cathodeelectrode 795. Each of these elements is formed as a layer and stackedor rolled together, with the two double sided adhesive and gas diffusionlayers 792 and 794 providing retentive adhesion. In further embodiments,the layers may be adhered in different manners, such as mechanicalfasteners or adhesive on different layers. In one embodiment, the layersare each adhered together, forming a gas tight stack.

The formation of the individual layers in the fuel cell stack will nowbe described, followed by an expanded view illustrating how the layersare assembled and used in a power generator. To form the anodeelectrode, an anode mask 800 in FIG. 8 may be used in one embodiment. Apolymer substrate 810, such as KAPTON, or PET is taughtly supported by aring 820. The ring 820 contains registration or alignment devices suchas pins 825 to allow precise positioning of the ring 820. The mask 800has multiple openings 840 to allow deposition of metal through the maskopenings 840 forming four pairs of anodes in this example.

Metal may be deposited such as by evaporation through the mask 800 ontoa 2 mil thick PET layer in one embodiment. A typical metallizationprocess may include an ion mill to clean the PET surface, followed by afew hundred angstrom (200-300 in one embodiment) of a Ti and/or Aladhesion layer, followed by 1-2 microns of Au (gold). Other conductivematerials may be used, but it is desirable that they be highlyconductive and corrosion resistant. Many other processes may be used forforming the conductive layer or layers of the anode. After deposition,the mask 800 is lifted, and a laser may be used to cut individualpatterns 910, 912, 914 and 916 as shown in FIG. 9. Each pattern containstwo anodes 920, 922 that have laser cut holes 925 to allow for gasdiffusion through the electrode. Each anode also has a tab 930 in thisembodiment, allowing for a series electrical connection of the two fuelcells when the fuel cell stack is conformed to a desired shape, such asa cylinder.

FIG. 10 is a blown up view of pattern 910, illustrating electrodes 920and 922 in larger form. In one embodiment, one side of the pattern 910may have an adhesive thereon for adhering to an anode support. In oneembodiment, the pattern is 2 mil thick PET with 1 mil adhesive, 200 ATi, and 1 um Au.

FIG. 11 illustrates an adhesive layer 1100 with an anode gas diffusionlayer. An alignment tab 1110 is provided in a desired location tofacilitate alignment with other layers. Adhesive layer 1100 has openings1120 and 1130 corresponding to the anodes 920 and 922. In oneembodiment, the adhesive layer may be 2 mil thick Kapton with 1 miladhesive on each side, with total thickness of 4 mils. The thickness mayvary considerably if desired and is approximately 0.1 mm thick in afurther embodiment. Openings 1120 and 1130 further comprise gasdiffusion layers, such as 4 to 6 mil thick carbon paper in oneembodiment.

An ion exchange membrane layer is illustrated in FIG. 12 at 1200. In oneembodiment, a frame 1210 of Kapton is used to support Nafion membranes1215 and 1220. Membranes 1215 and 1220 are positioned to align with1120, 1130 and anodes 920 and 922 when assembled. The membranes 1220 and1215 may be 1 mil thick Nafion NRE211 with 0.5 mg/cm² of carbonsupported platinum electrodes. Different thicknesses of membranes andother layers may be used in further embodiments consistent withretaining a desired flexibility for the fuel cell stack. In oneembodiment, two cells are being formed with the multiple layers thatwill be coupled in series when assembled.

FIG. 13 at 1300 represents a double sided adhesive layer including a gasdiffusion layer for the cathode layer. It may be similar to that shownat 1100 in FIG. 11, including two openings 1320 and 1330 for alignmentwith the cathodes in the next layer. In one embodiment, the adhesivelayer may be 2 mil thick Kapton with 1 mil adhesive on each side, withtotal thickness of 4 mils. The thickness may very considerably ifdesired and is approximately 0.1 mm thick in a further embodiment.Openings 1320 and 1330 further comprise gas diffusion layers, such as 4to 6 mil thick carbon paper in one embodiment.

FIG. 14 illustrates a cathode pattern 1410 having electrodes 1420 and1422 shown with holes similar to those in the anodes described earlier.In one embodiment, the pattern is 2 mil thick PET with 1 mil adhesive,200 A Ti, and 1 um Au. A connector 1430 is shown facilitating couplingof the resulting fuel cells in series. Pattern 1410 may be formed in thesame manner as the anode pattern using mask shown at 1500 in FIG. 15,resulting in multiple patterns which are laser cut with holes and cutinto separate patters in FIG. 16 at 1600.

The layers of the fuel cell stack described above may be assembled inmany different ways. In one embodiment, individual layers may be rolledone by one onto an anode support using a dual roller fixture. In afurther embodiment, the layers may be stacked on a planar surface, andthen rolled as a stack onto an anode support 1710 as illustrated in FIG.17, which is an exploded perspective view of a fuel cell stack and powergenerator according to an example embodiment.

In one embodiment, the order of the fuel cell stack layers is asdescribed above, starting with the anode electrode layer 1720, theadhesive and anode gas diffusion layer, the membrane, the adhesive andcathode gas diffusion layer, followed by the cathode electrode 1730. Theanode support 1710 is a rigid cylinder on which the anode electrode isadhered, and supports the stack and compresses it to a specified degreeagainst the inside of container 745.

The resulting two cells are electrically coupled in series in oneembodiment by virtue of the electrode designs. Tab 930 on anode 920 andtab 1430 on cathode 1422 are electrically connected. A tab 1440electrically connects cathode 1420 to anode support 1710. Container 745is electrically connected to anode support 1710 and functions as thecathode terminal of the power generator. Tab 940 is connectedelectrically to anode plate 230 which functions as the anode terminal ofthe power generator. The anode support 1710, with the fuel cell stacklayers adhered to it is inserted into a sliding valve 1750 which isinserted into a fixed valve 1760, followed by the fuel and membrane1770. FIG. 17 illustrates an efficient and convenient method by which apower generator may be assembled.

The Abstract is provided to comply with 37 C.F.R. §1.72(b) to allow thereader to quickly ascertain the nature and gist of the technicaldisclosure. The Abstract is submitted with the understanding that itwill not be used to interpret or limit the scope or meaning of theclaims.

1. (canceled)
 2. A method of forming a power generator, the methodcomprising: forming a container having a desired shape; placing ahydrogen producing fuel within the container; adding a sliding valvearrangement within the container and positioned around the hydrogenproducing fuel; coupling a pressure responsive diaphragm to the slidingvalve arrangement; wrapping a fuel cell stack around an anode supportand sliding valve arrangement within the container, the fuel cell stackhaving a cathode electrode layer for exposure to oxygen and an anodeelectrode layer for exposure to hydrogen; electrically coupling thecontainer to the cathode electrode layer of the fuel cell stack suchthat a desired portion of the container forms an exposed cathode; andforming an exposed anode electrically coupled to the anode electrodelayer of the fuel cell stack and supported by the container such that atleast a portion of it is exposed on the outside of the container andspaced apart from the exposed cathode.
 3. The method of claim 2 whereinthe fuel cell stack is formed by the method comprising: forming theanode electrode layer including an anode electrode portion and anon-electrode portion; forming an anode double sided adhesive layerhaving a non-adhesive gas diffusion layer therein, said double sidedadhesive layer adhered on one side to the anode electrode layer suchthat a portion of the anode electrode is in contact with the anode gasdiffusion layer; forming an ion exchange membrane layer having an ionexchange membrane in an opening therein, said ion exchange membranealigned with the non-adhesive anode gas diffusion layer in the openingin the anode double sided adhesive layer, said ion exchange membranelayer adhered on a first side to the side of the double sided adhesivelayer opposite the anode electrode layer; forming a cathode double sidedadhesive layer having a non-adhesive cathode gas diffusion layer in anopening therein, said cathode gas diffusion layer aligned with the ionexchange membrane, said double sided adhesive layer adhered on one sideto a second side of the ion exchange membrane; forming the cathodeelectrode layer including a cathode electrode portion and anon-electrode portion adhered to the cathode double sided adhesive layerand having a non-adhesive cathode gas diffusion layer in an openingtherein, on the side opposite the ion exchange membrane; pressing theformed layers together as parallel adjacent planes rolled to form aflexible fuel cell stack, the parallel adjacent planes sufficientlyflexible to be conformed into a cylindrical shape; conforming theflexible fuel cell stack to a cylindrical shape to form a cylindricalfuel cell stack; and adhering the cylindrical fuel cell stack around arigid cylindrical anode support.
 4. The method of claim 3 wherein thethickness of the stack is approximately 1mm or less.
 5. The method ofclaim 4 wherein the stack includes two series connected fuel cells. 6.The method of claim 4 wherein the anode electrode layer and the cathodeelectrode layer have multiple through holes.
 7. The method of claim 4wherein each of the layers are adhered together.
 8. The method of claim4 wherein the anode electrode layer and the cathode electrode layer areformed by depositing a titanium or aluminum adhesion layer on a polymersubstrate and depositing gold on such layer and by forming multipleholes through both the anode and the cathode layers.
 9. The method ofclaim 8 wherein the anode electrode layer is formed with fuel cellanodes, each with a tab for facilitating an electrical series connectionbetween two fuel cells in the fuel cell stack.
 10. A method of forming apower generator, the method comprising: forming a container having adesired shape; placing a hydrogen producing fuel within the container;adding a sliding valve arrangement within the container and positionedaround the hydrogen producing fuel; coupling a pressure responsivediaphragm to the sliding valve arrangement; wrapping a fuel cell stackaround the sliding valve arrangement within the container, the fuel cellstack formed by a method comprising: forming an anode electrode layercomprising an anode electrode portion and a non-electrode portion;forming an anode double sided adhesive layer having a non-adhesive gasdiffusion layer therein, said double sided adhesive layer adhered on oneside to the anode electrode layer such that a portion of the anodeelectrode is in contact with the anode gas diffusion layer; forming anion exchange membrane layer having an ion exchange membrane in anopening therein, said ion exchange membrane aligned with thenon-adhesive anode gas diffusion layer in the opening in the anodedouble sided adhesive layer, said ion exchange membrane layer adhered ona first side to the side of the double sided adhesive layer opposite theanode electrode layer; forming a cathode double sided adhesive layerhaving a non-adhesive cathode gas diffusion layer in an opening therein,said cathode gas diffusion layer aligned with the ion exchange membrane,said double sided adhesive layer adhered on one side to a second side ofthe ion exchange membrane; forming a cathode electrode layer comprisinga cathode electrode portion and a non-electrode portion adhered to thecathode double sided adhesive layer and having a non-adhesive cathodegas diffusion layer in an opening therein, on the side opposite the ionexchange membrane; pressing the formed layers together as paralleladjacent planes rolled to form a flexible fuel cell stack, the paralleladjacent planes sufficiently flexible to be conformed into a cylindricalshape; conforming the flexible fuel cell stack to a cylindrical shape toform a cylindrical fuel cell stack; and adhering the cylindrical fuelcell stack around a rigid cylindrical anode support electricallycoupling the container to the cathode electrode of the fuel cell stacksuch that a desired portion of the container forms a cathode; andforming an anode electrically coupled to the anode electrode of the fuelcell stack and supported by the container such that at least a portionof it is exposed on the outside of the container spaced apart from theexposed cathode.
 11. The method of claim 10 wherein the hydrogenproducing fuel is formed by stacking multiple fissurized pellets intothe container wherein the stack of pellets is encapsulated in a watervapor and hydrogen permeable, liquid water impermeable membrane.